Integrity Service Excellence
Metamaterials and Metasurfaces for Heat
Transport Control
December 13 2016
Augustine UrbasMaterials and Manufacturing Directorate
Metamaterials
•Overview of structured materials•Examples of controlling thermal emission•Controlled heat transport with metamaterials
• Conventional dielectric materials have µ>1 and ε>1 and we don’t typically find materials with µ=ε.
• The interaction with the magnetic field decreases as frequency increases and µ 1
• Generally limited in choice of materials to available values/ranges
Electromagnetic properties of materials
Metamaterials Design Space
µ
Sub-λimaging, focusing
+,-
-,+
-,-
ε
Conformal Antennas
+,+
Signal Couplers
Opt
ical
Filt
er
Mat
eria
ls
Challenges to creating useful new properties
•Useful and well defined effective materials properties
•Mitigation/compensation of Losses
Other attributes to consider
•Coupled properties•Nonlinear effects•Graded structures
a
22 arf cπ=
rctc
Lc
dc
HinHex
Inductor
Capacitor
R
L
C
Artificial Material Response
PRL 84, 2184, 2001 Physics today, June 2004
Meta inspired RF photonic Modulator
• RF resonator to concentrate fields
• High efficiency EO materials to mix RF with optical carrier– Inorganics– Organics provide
more flexibility
wg
•Also potential for materials that modify resonant properties of Meta stuctures to tune properties
•Optical Magnetism and LC materials are potential candidates
•SRR sensitivity to changes of gap materials properties.•25 GHz/mm^3RIU sensitivity to gap material•10^6 stronger than volumetric sensitivity to surrounding media
6.0 6.2 6.4 6.6 6.8 7.0 7.2
0.2
0.4
0.6
0.8
1.0
Norm
alize
d Tr
ansm
issio
n of
x-p
olar
ized
inpu
tFrequency GHz
BL006 aligned in y-direction BL006 aligned in y-direction
and z-direction in gap BL006 aligned in z-direction
Sensitivity of Metamaterials
4.2 mm
0.16 mm
2.2 mm
0.1 mm 1 mm
E,x
k,z
H,y
LC
Liquid Crystal RF Beam Steering
• Liquid Crystal material used to tune interaction between ground plane and metal patch
• Changed phase of reflected RF signal
• Pixelated array steerable reflector
Radu Marin “Investigations on liquid crystal reconfigurable …” 2008 Thesis, TU Darmstadt
Metamaterial Steerable Antennas
•Dynamic metamaterials can allow for tunable and steerable antennas
•This may make RF systems simpler and enable cheap wifi on commercial airlines
Kymeta Inc.
Portable Satellite Terminal
Negative Refractive Index at Optical Wavelengths Science 351 Jan2007Soukoulis, Linden and Wegener
Metamaterials: Size scales
11
Unit Cell Design
Metamaterial Structural Scales
SubunitD
Plasmonicspe
rmitt
ivity ε0
ωp
2
2
1ωω
ε p−=
mz
dz
mz
dz
kk
εε
−=
•Surface waves at the interface between materials with ε>0 and ε
a
22 arf cπ=
rctc
Lc
dc
HinHex
Inductor
Capacitor
R
L
C
Artificial Material Response
PRL 84, 2184, 2001 Physics today, June 2004
Transformation Optics
x′ = x′(x)
Transformation optics and metamaterials, Chen, Chan, Sheng,Nature Materials | VOL 9 | MAY 2010 | p387
Texturing of ε and µ can mimic spatial coordinate tranform
∇ × Eʹ + iωμʹHʹ = 0∇ × Hʹ – iωεʹEʹ = 0
∇ × E + iωμH = 0∇ × H – iωεE = 0
Transformation Optics:Luneburg Lens
Original profile with curved focal plane
Transform with flat focal plane
Constructed Lens
Unit cell
Metamaterial Flat Lenses
• In the optical domain, small crescents produce geometry dependent scattering phase
• Flat lenses created with single layer of tailored scatterers, spatially mapped to create the appropriate phase funtion to mimic a solid lens
•Capasso et al. 2012
18DISTRIBUTION A Approved for Public Release; distribution unlimited
Planar Focusing Lens
15µm30µm
Without lens
With lens
• Semiconductor based, low-loss zero-index optical metamaterials
• Demonstration of enhanced directional emission from quantum dots (QDs) within the ZIM.– Jason Valentine
(Vanderbilt University)
SEM of Si based ZIM (left), angular confinement of transmission (center) and confinement of QD emission within the ZIM (right).
Cross-section Enhancement
Number of Layers
Calculated Ratio*
Measured Ratio
2 9.57 4.84 ± 14.7
4 2.94 2.28 ±3 .7
6 1.49 1.72 ± 5.61
8 1 1*for n = 1.5, but changes little from n = 1.3 – 1.7
Predicted slope (COMSOL) = -0.477 ± 0.020 layer-1
Measured slope = -0.434 ± 0.18 layer-1
Fit using y = b + Aemx
Electric field calculated in COMSOL
Murphy et al, Langmuir, 2012, submitted
TPA Enhancement and Predicted Relationship
Micro Spiral Plasmonic Lens/Circular Polarizer for Polarimetry
Left: Traditional linear micro-polarizers on a focal plane arrayRight 3: planned spiral circular polarizers/lenses to be deposited on a FPA, and simulation showing selective focusing of a particular circular polarization. Extinction ratios of >40 are possible with energy efficiencies around 30%.
200 nm thick Gold filmSlot width 200 nm
InSb
SiO TiAuGlueSi
ROIC
FPA pixel morphology, spirals will be milled into gold layer and centered on InSb island. Light from top will then be selectively focused into InSb pixel.
21
IR polarizer
• Recent experimental study in spiral MMs
• High efficiency CP in broad band IR
• Reflective, novel detection schemes?
• Few percent integrated loss
• 3.5um – 8um by design• No competing
technology (?)
Science 325, 1513 (2009);Gansel, Wegener, et al.Circular PolarizerGold Helix Photonic Metamaterial as Broadband
Four-Fold Approach:1. Utilize the high scattering cross-sections of
metallic nanoparticles to increase the path length in a photovoltaic cells.
2. Focus the high electric near-fields of resonant nanoparticles to enhance the media’s photophysical properties.
3. Design a cell with the absorbing metal nanoparticles as the active hot electron injector.
4. Couple incoming light into horizontal block mode resonances to trap light into guided modes in the cell.
Plasmonic Enhancement of Solar Energy Generation
Objective: Increase power output from lightweight, flexible solar cells for AF needs.
Metamaterials for Improved Solar Power Generation
Scattering
Absorption Block Mode Propagation
Electric Near-Field
ICMSE will be used to design sub-wavelength structures to trap light with the polymer solar cell.
Stamped Film
ControlA game-changing technology that harnesses tunable plasmonic nanoparticles as the active PV species.
Plasmonic nanoparticles outperform current anti-reflection coatings on solar cells.
Localized near-field enhancements largely influence the photophysical properties of the local media.
Nanoparticle / Organic Polymer PV Composite
1400 1200 1000 800 600
-600
-400
-200
0
200
400
600
800
1000
dt/T
(ppm
)
Wavelength (nm)
50% Ag NP sol, [OAm] = 87mM 20 % Ag NP sol, [OAm] = 35mM 10% Ag NP sol, [OAm] = 17mM 0 Ag NP sol, [OAm] = 0
Thermal control for space systems
Visible and IR(EO imaging)
M/LWIR(thermal)
Visible and NIR/SWIR (solar)
RF(Comm)
Non-Directional IR Emittance
solar flux in
solar flux out
aluminum panel
thermal bottleneck
heat radiated away hemispherically Earthshine/
albedo
Directionally-Tailored IR Emittance
solar flux in
solar flux out
heat radiated away directionally
30° radiance angle
Earthshine/albedo
structural MM panel?
Reduced conduction
Goal is to tune angle and spectrum of emission to utilize more surface area for thermal control
•A non-dense carpet of nanotubes was analyzed by its effective index to determine the nature of its record setting absorption•Possible application in TPV
• Modeling with MG to get effective medium properties shows an index close to 1 providing for a total reflectance of
AFM image of SiC grating designed for peak emissivity at λ = 11.36 um
NATURE |VOL 416 | 7 MARCH 2002
Emission from surface heated to 500 oC as a function of detector position for λ =11.36 um. Red line is experimental data, green is predicted.
Coherent Direction of Thermal Radiation from Surfaces
Photonic Structures for Emissivity Control
Enhanced Emission
Eggelston et al. PNAS 2014
Radiative Cooling for Thermal Control
Temp 300k
Air flow convective transfer
Radiative heat load
Radiative cooling
Temp 5000k
Passive radiative cooling below ambient air temperature under direct sunlight, AP Raman, MA Anoma, L Zhu, E Rephaeli, S Fan. Nature 515, 54, 2014
• Control of thermal surfaces in radiative heating dominated environments can be important
Bio-Inspired Photonic Heat Shields
• Examples of biological control of temperature by controlled daytime radiative cooling.
• Balance of reflection and absorption and thermal properties to reject load, radiativelycool and insulate. Keeping Cool: Enhanced optical reflection and heat dissipation in silver ants, NN
Shi, CC Tsai, F. Camino, GD Bernard, N. Yu, R. Wehner. Science 349, 298, 2015
• Synthetic example made of alumina mimics bio-system
• Performing combined modeling and experimental studies to control heating
Kyoungsik Kim, Yonsei U.
Next generation thermal barrier coating
Siegel R, Spuckler CM. 1998. Mater. Sci. Eng. A 245:150–59
SOTA thermal barrier coatings for jet turbines are IR transparent
Higher gas temperatures in future jet engines will need to accommodate increased radiated power to TBC substrate
(Clarke, Levi Ann. Rev. Mat. Sci. 2003)
Two approaches:-absorb IR
-convert to lower E phonons-re-emit at longer λ
-reflect IR
Thermal Barrier Coaings to Reduce Heat Transfer
http://science.howstuffworks.com/flight-pictures.htmhttp://science.howstuffworks.com/flight-pictures.htm
Nonlinear plasmonics: Nitrides
• Nitride materials are useful plasmonicmaterials
• More resilient for nonlinear optical systems
• Transition metal nitride– Nonstoichiometric semiconductor – Cubic crystal structure– Compatible with CMOS technology
• Plasmonic material– More robust than gold and silver
• High hardness• Chemically stable• High 𝑇𝑇𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚 >2900o C
– Large free carrier concentration 1022𝑐𝑐𝑚𝑚−3• 10x concentration of TCOs• Same order of magnitude as Au• Very large optical nonlinearity
• Tunable optical properties– Stoichiometry– Temperature of deposition– Substrate
Thin Film Titanium Nitride34
Artificially Structured Acoustic Materials
1. Phononic Crystals
Maldovan, M. Nature 2013, 503, (7475), 209- 217 http://emps.exeter.ac.uk/physics-astronomy/
Dispersion Relation
Maldovan, M. Nature 2013, 503, (7475), 209- 217
Phononic Crystals
343 m 34 cm 343 nm.34 mm 3.43 Åa
Speed of sound in air = 343.2 meters per second
Artificially Structured Acoustic Materials
2. Acoustic Metamaterials (local response)
• Metamaterials are artificial structures, with unconventional effective properties.
• A metamaterial structure is typically 10 or more times smaller than the smallest acoustic wavelength being manipulated.
• Do not need to be periodic
• Negative ρ or β means that at certain frequencies the medium expands when experiencing compression (negative modulus), and accelerates to the left when being pushed to the right (negative density)
Bulk modulus (K): compressional stiffness of the materialmass density (ρ): controls wave propagation
Nature Reviews Materials 1, 16001 (2016)
Applications in acoustic absorption, bend sound the wrong way, acoustically conceal an object
Slide Number 1Metamaterials Electromagnetic properties �of materialsMetamaterials Design SpaceArtificial Material ResponseMeta inspired RF photonic ModulatorSensitivity of MetamaterialsLiquid Crystal RF Beam SteeringMetamaterial Steerable AntennasSlide Number 10Unit Cell DesignSlide Number 12PlasmonicsArtificial Material ResponseTransformation OpticsTransformation Optics:�Luneburg LensMetamaterial Flat LensesPlanar Focusing LensCross-section EnhancementSlide Number 20IR polarizerSlide Number 22Slide Number 23Thermal control for space systems Non-Directional IR EmittanceDirectionally-Tailored IR EmittanceMetamaterials:�Extreme AbsorbersPhotonic Structures for Emissivity ControlEnhanced EmissionRadiative Cooling for Thermal ControlBio-Inspired Photonic Heat ShieldsThermal Barrier Coaings to Reduce Heat TransferNonlinear plasmonics: NitridesThin Film Titanium NitrideSlide Number 35Slide Number 36Slide Number 37Slide Number 38
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